Horizontal table type filter elements with timing means



Aug. 20, 1968 l. MINI 3,397,787

- HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Filed May 16.1967 '7 Sheets- Sheet 1 FIG. 1

Aug. 20, 1968 l. MINI 3,397,787

HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Filed May 16,1967 7 Sheets- Sheet 2 FIG 2A HG 2 8 100. 10C 108 10d 10b 11a He He 11d11h I. MINI Aug. 20, 1968 HORIZONTAL TABLE TYPE FILTER ELEMENTS WITHTIMING MEANS '7 Sheets-Sheet 7 Filed May 16, 1967 Aug. 20, 1968 l. MINI3,397,787

HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Filed May 16,1967 7 Sheets- Sheet 4 Aug. 20, 1968 l. MINI 3,397,787

HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Filed May 16,1967 '7 Sheets-Sheet 5 lle 3/e 50a l. MINI 3,397,787

HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Aug. 20, 1968 '7Sheets- Sheet 6 Filed May 16, 1967 FIG.5B

Aug. 20, 1968 I. MINI 3,397,787

HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Filed May 16,1967 7 Sheets-Sheet '7 FIG. 6

-35a 35b -35c 35d 35e I T I I I II I I I 1 II I III I I I I I II I 0 :1ea 0 0 0 uum 5 "am 38; N 88 3" $7.0

I Q) Q 1, E s g m N m 01% 4: a) at!) 3w 0 N (O a, 3 ,2 gm w w LO g f V TV" United States Patent 01 hce Patented Aug. 20, 1968 3,397,787HORIZONTAL TABLE TYPE FILTER ELEMENTS WITH TIMING MEANS Iti Mini, Milan,Italy, assignor to Montecatini Edison S.p.A., Milan, Italy, acorporation of Italy Continuation-impart of application Ser. No.466,211, June 23, 1965. This application May 16, 1967, Ser. No. 642,643Claims priority, application Italy, June 30, 1964, 14,261/ 64 11 Claims.(Cl. 210-139) ABSTRACT OF THE DISCLOSURE A filter assembly havingmultiple, horizontal, vacuum operated, table type filter elements andhaving a feeder distributor stage which supplies slurry and n differentwashings to n+1 filter elements while another filter element remainsunfed and is overturned to discharge residue, and having a collectorstage which collects each filtrate separately in n+1 vessels, and timingmeans to operate the filter assembly continuously, each filter elementreceiving the different fluids and being overturned in sequence one stepahead of or behind of another element.

Specification This is a continuation-in-part of my application Ser. No.466,211, filed June 23, 1965, now abandoned.

My invention relates to filters of the continuous vacuum type. Moreparticularly, it relates to such improved filters suitable for use inmultiple backwashings, especially in situations where it is desired toseparate a liquid from a quite fine solid and where it is necessary toefifect a thorough washing with only a relatively moderate amount ofadditional liquid.

At present there are many types of filters which are utilized for vacuumfiltration and subsequent washings. Such types include discontinuousfilters, drum filters, continuous belt filters, continuous rotatingfilters, belt of tray filters, and rotating trays filters. All of thesetypes of filters have in common the characteristic that the filteringsurface moves with the filter cake during filtration While the slurryand washing liquids are fed at fixed positions.

Of the above set forth filter types, the drum filters, which have beenin use the longest, are probably the simplest in construction but theycan be employed only for about one washing and are not suitable for usewith various types of slurry materials, particularly phosphoric acid.The other filters set forth hereinabove enable a filtration of slurrytype materials with several, i.e., normally about three, subsequentwashings of the cake. However, of these filters, the continuous belt oftrays and continuous rotating trays filter types do not effect asatisfactory separation of liquids and, consequently, the filtrateresulting from the first filtration becomes mixed with the washings andis thus diluted.

The only filters presently available for accomplishing efiicient resultsin practice are those of the belt of trays and rotating trays type. Inthese types of filters, in the belt of trays type, the respective traystraverse in a horizontal linear movement, and in the rotating traystype, the trays traverse in a rotary movement. The trays first receivethe slurry and then receive the subsequent backwashings, the filtersbeing subjected to a vacuum during filtration.

Both trays type filters require a complex control and guidance systemfor removing the trays. Furthermore, with regard to the rotating traystype filters, there are further required control and guide means forperiodically overturning the trays thereof. Also in the rotating traystype filters, the rotating members have to be constituted of noblemetals or metals not subject to corrosion, whereby there resultsexpensive apparatus.

Because of the required movement of the trays in the filtering process,sliding seal members are required in the apparatus for collectingvarious kinds of filtered liquids from the trays, such sliding sealmembers being subjected to wear and undergoing vacuum losses inoperation. Furthermore, it is periodically necessary to halt theoperation of the filters and consequently the production processes inwhich they are being employed (except when standby filter apparatus maybe available) to lubricate them, change their filter cloths, normallymaintain them, and wash the elements transporting the filtrate in orderto remove solid deposits therefrom. The latter Washing requirementparticularly obtains in the processing of phosphoric acid in which theonly slightly soluble calcium salt deposits have to be removed. In thebelt of trays type filters, a further disadvantage is presented in thatthey do not provide satisfactorily large working surfaces andconsequently more filter units of this type are required in processinglarge quantities of material. There exists, at present, a still furthertype filter, similar to the rotating trays type filter, but difieringtherefrom in that, during its operation, its trays remain stationary,while the feeder and discharge mechanisms therefor are rotated. However,these reversals of rotating functions in this type of filter as comparedwith the hereinabove described rotating trays type filter, do notovercome the deficiencies therein and the same disadvantages arepresented thereby as by the types of filters outlined above.

Accordingly, it is an important object of this invention to provide atrays type filter which is mechanically simple as compared to known typefilters used for the same purpose thereby effecting reduced installationand maintenance costs.

It is another object to provide a filter constructed in accordance withthe preceding object which presents comparatively large surfaces.

It is a further object to provide a filter in accordance with thepreceding objects wherein deposits do not form and the need for haltinga production process for normal maintenance, lubrication or changing ofcloths in the filter is eliminated, uninterrupted continuous productionnot being dependent upon the presence of standby filter apparatus.

It is still another object to provide a filter in accordance with thepreceding objects wherein relative movements between feeding members andfiltering elements and the need for sliding seal members in theseparation of liquids are completely eliminated, thereby making thefilter considerably more vacuum-tight than has heretofore been possible.

It is still a further object to provide a filter suitable for use inenabling multiple backwashings Particularly in situations where a liquidis to be separated from a very fine solid, and a thorough washing withonly moderate amounts of additional liquid.

It is yet another object to provide a filter in accordance with thepreceding objects which is particularly suited for the separation, by awet process, of phosphoric acid, and for other filtering applications inthe chemical industry.

Generally speaking and in accordance with the invention, there isprovided a continuously operative vacuum filter capable of effecting afiltration of a slurry and a given number of subsequent backwashings offilter cake with the aforesaid given number of different Washing fluidscomprising a feeder-distributor stage, a vacuum filtration stage, acollector and separator stage, and a timer for controlling thesynchronization of the operation of the various stages. The vacuumfiltration stage comprises a chosen number of filter elements, suchchosen number exceeding the given number by at least two, each of thefilter elements including a normally upright vessel, outlet means fordischarging filtrate fluid therefrom adapted for connection to a vacuumsource and control means associated with the vessel and operative to beactuated to place the vessel in an overturned position and restore itfrom the overturned back to the upright position. The feederdistributorstage comprises means for separately receiving the slurry and each ofthe aforesaid washing fluids, means for concurrently feeding one of theslurry and the washing fluids to each of the respective filter elementsduring a given time period which is an equal subdivision of a time cycleconsisting of the aforesaid chosen number of time periods and forsequentially feeding the slurry and the washing fluids in apredetermined order to each of the filter elements whereby during eachtime cycle, each filter element sequentially receives the slurry andeach of the washing fluids in the aforesaid predetermined order and isunfed during one period of the time cycle and whereby the slurry andeach of the washing fluids are respectively sequentially fed todifferent filter elements respectively and each of the filter elementsis respectively unfed in successively occurring time periods. Thecollector and separator stage receives the fluid filtrate outputs fromthe filter elements and separately collects them, the collector andseparator stage including the aforesaid chosen number less one ofcollecting vessels and means for directing the respective same fluidfrom the filter elements fluid outputs into only respective ones of thecollecting vessels. The timer controls the sequential feeding of thefluids to the filter elements and controls the actuation of the filterelement vessels control means during their respective unfed periods.

The above mentioned and more specific objects and features of thisinvention will be apparent from, and will be mentioned in the followingdescription of the filter according to the invention shown by way ofexample in the accompanying drawing in which:

FIG. 1 is a diagrammatic depiction of a filter constructed in accordancewith the principles of the invention;

FIGS. 2A, 2B and 2C schematically show an illustrative embodiment of afeeder-distributor stage suitable for use in the filter shown in FIG. 1;

FIG. 3 shows another illustrative embodiment of a feeder-distributorstage suitable for use in the filter of FIG. 1;

FIG. 4 is a schematic view of a structure suitable for use as a filterelement in the filtration stage of the filter of FIG. 1;

FIG. 4A is a diagrammatic view of the operating circuit of the timer ofFIG. 1;

FIGS. 4B and 4C are diagrammatic views of two of the rotary discs of thetimer shown in FIG. 4A, showing various contact settings;

FIGS. 5A, 5B and 5C schematically show an embodiment of acollector-separator suitable for use as the collector stage of thefilter of FIG. 1; and

FIG. 6 is a schematic depiction of another illustrative embodiment of acollector-separator suitable for use as the collector stage of thefilter of FIG. 1.

Prior to describing the structure and operation of the invention asdepicted in the accompanying drawing, there follows hereinbelow aglossary of terms employed herein to describe and designate the variousmaterials and operations respectively pertinent thereto.

Glossary SlurryThe suspension in which the liquid component is to beseparated from the solids component.

FiltrateP-The liquid constituting the slurry after the solid has beenseparated therefrom.

Fresh solventThe fresh liquid utilized for backwashing the cake (waterin the case of phosphoric acid).

First washingThe liquid resulting from the Washing of the cake withfresh solvent.

Second washingThe liquid resulting from the washing of the cake with thefirst washing.

Third washingThe liquid resulting from the washing of the cake with thesecond washing. Also referred to as the washing solution In FIG. 1wherein there is schematically depicted 'a filter constructed inaccordance with the principles of the invention, the filter can beconceptually described as comprising four coacting components, viz., afeeder and dis tributor stage 1, a vacuum filtration stage 2, acollectorseparator stage 3, and a timer 4.

In considering the operation of this filter, if it is assumed thatfiltration has proceeded to the point wherein all the components as setforth in the glossary hereinabove are being produced and handled by thefilter, a distributor D in feeder and distributor stage 1 has fedthereto the slurry to be filtered and the fresh solvent respectivelydesignated by the letters A and B, and the first and second washingsrecycled from the output of collector stage 3.

Through the operation of distributor D, the four dif- I ferent fluidsintroduced into distributor D are fed therefrom to the respective filterelements or groups of filter elements comprising the filtration stage 2,four of these filter elements being designated with the notations F to Frespectively. As will be further explained hereinbelow, the fourdifferent separated fluids from distributor D are fed therefromcyclically in a synchronized timing sequence to the filter elements invacuum filtration stage 2. It is noted that filtration stage 2 is shownas including a fifth and overturned filter element. As will be furtherexplained hereinbelow, such fifth element is utilized to receive thecake and to be overturned to discharge the cake to conveying apparatus.

To further illustrate the operation of feeder and distributor stage 1and vacuum filtration stage 2, let it be assumed that filter elements Fto R; at the same point in a given cycle have respectively been feedslurry, fresh solvent, first washing and second washing simultaneouslyand the fifth filter element has cake therein. At the next point in thiscycle, filter elements F F F and the fifth filter element simultaneouslyreceive slurry, fresh solvent, first washing and second washingrespectively and filter element F is unfed. The notations V V V and V;are shown as designating the fluid outputs of filter elements F to FHowever, as explained hereinabove, all five filter elements sequentiallycyclically receive each of the respective fluids whereby thedesignations V to V illustrate a point in a cycle when the fifth elementis unfed. The four fluid outputs V to V; of vacuum filtration stage 2are the filtrate and the first, second and third washings. As will befurther explained hereinbelow, means are included in filtration stage 2to cut off the vacuum from the filter element which is unfed at a givenpoint in the cycle and to overturn it to cause it to discharge the cake.

-In collector stage 3, the fluids V to V; are received and separated,the first and second washings being recycled by being fed back todistributor D, the filtrate and the third washing, or washing solution,designated by the notations Y and Z, being eliminated from thefiltration cycle.

It is realized that at the initiation of a filtration process, onlyfresh solvent and slurry are first available for introduction intodistributor D, As the process proceeds, at a succeeding point therein,first washing solution is produced from the output of collector stage 3,the feeding of such first washing solution back to distributor Deffecting the production of second washing solution. At this point, allof the fluids of the filtration cycle are present.

The timer 4 is constructed to synchronously control the timing of theoperation of feeder and distributor stage 1 and collector-separatorstage 3, the timing for cutting off the vacuum from the unfed filterelement in the vacuum filtration stage 2 and also controls thesequential feeding of the filter elements cyclically with the differentfiltration products to insure that a feeding to a filter element takesplace only when the immediately preceding material fed to such elementhas been completely removed therefrom.

A sixth standby filter element (not shown) may be utilized to enable theremoval of one of the operating filter elements for changing its cloth,or maintenance or lubrication thereof without materially interruptin theproduction process which includes the filtration process.

It is to be appreciated from the foregoing description that since thedifferent liquids sequentially pass through the respective components ofthe filter, particularly the filter elements which are subjected to avacuum, deposit forming during the filtration of the slurry which is adetrimental factor in the operation of known filters is prevented withthe filter of the invention since any deposit about to be formed thereinis rapidly dissolved by the receiving thereby of the next liquid fedthereto in the sequential feeding cycle. Thus, one of the most frequentcauses of periodic halts in the operation of known filters with itsconsequent interruption of production is eliminated.

In FIGS. 2, 2A, 2B and 2C wherein there is schematically depicted anillustrative embodiment of a feeder-distributor constructed inaccordance with the principles of the invention, a cylindrical vessel 1which may have a frusto-conical lower portion to facilitate fluid flowtherein is subdivided into substantially five equal compartments byradially disposed bafiles 2a, 2b, 2c, 2d and 2e. Vessel 1' has fluidintroduced thereinto by four pipes schematically depicted by arrows 3a,3b, 3c and 3d. As shown in FIG. 2B, pipes 3a, 3b, 3c and 3d are disposedwhereby they are radially equidistant from the central vertical axis ofvessel 1' and are equiangularly displaced from each other, i.e. by 72.Through pipes 3a, 3b, 3c and 3d, slurry, fresh solvent, and first andsecond washings are introduced into vessel 1, vessel 1 being rotated ina horizontal plane by suitable means such as a crown gear 4 whichcooperates with a gear 5 that is operated by a suitable control whichmay be mechanical and is schematically depicted by element'6.

The element 6 is basically formed by an eletcric motor and a mechanicalreduction system, for instance gears, V-belts or chains, designed toprovide a ratio of reduction to obtain a complete rotation of vessel 1'in the most convenient time for best operation, generally from two tosix minutes. The time adjustment can be obtained by suitably adjustinthe control element 6, e.g. by changing the diameter of the gears, thepulleys or the V-belts. The timer 4 of FIG. 1 performs a complete cycleduring a complete revolution of vessel 1' and is electrically ormechanically connected to the control 6.

From the base of vessel 1', there emerge five pipes, shown schematicallyas arrows 7a, 7b, 7c, 7d and 7e, these pipes being attached to vessel 1'whereby they are rotated therewith, each of these five pipesrespectively communciating with one of the five compartments in vessel 1as defined by bafiles 2a, 2b, 2c, 2d and 22. Each of pipes 701 to 7erespectively communicates with and otherwise feeds fixed ducts 8a, 8b,8c, 8d and 8e, ducts 8a to Sc being concentrically disposed in asubstantially horizontal planar array. Five pipes, as shown by arrows9a, 9b, 9c, 9d and 9e communicate with and lead from ducts 8a to Sc tocorrespondingly feed five vessel 10a, 10b, 10c, 10d and 106, which inturn feed the five filtering elements schematically shown as valves 11a,11b, 11c, 11d and 11e.

In considering the operation of the distributor shown in FIGS. 2A, 2Band 2C, it is seen that during the time for a one-fifth turn of vessel1, four of the five compartments therein as defined by baflies 2a to 2eand consequently four of the five pipes 7a to 72, four of the five ducts8a to 8e, four of the five pipes 9a to 92, and four of the five vessels10a to -10e are fed with the same respective fluid from pipes 3a to 3drespectively while the remaining respective fifth vessels and pipes arenot fed. During the next ouefifth turn of vessel 1, the respective unfedfifth compartment of vessel 1' and the corresponding pipes and vesselassociated therewith receives a fluid. It is assumed that the latterfluid is the fresh slurry, the one that had the one that had receviedthe second washing now receives received the fresh slurry now receivesthe second washing, the first washing, the one that had received thefirst washillg receives the fresh solvent, and the one that had receivedthe fresh solvent now remains unfed.

The valves 11a to 112, placed at the outlets of vessels 19a to 10 arecontrolled to be automatically opened and closed in accordance with agiven timing arrangement by timer 4, their opening and closing timesbeing so chosen whereby fluids are discharged from vessels 10a to 102through valves 11a to 11s into the vessels of the filter elements whenthe fluid introduced into the filter element vessels in the immediatelyproceding one-fifth of the cycle have been completely removed therefromto avoid the mixing of respective entering and departing fluids in thefilter element vessels.

It is thus seen that with the distributor of FIGS. 2A to 2C, each of thefive filter elements can sequentially receive slurry, second Washing,first washing and fresh solvent in four-fifths of a cycle and in theremaining fifth of a cycle be unfed with a fluid whereby it candischarge the washed cake. It is further seen that a different fifth ofthe cycle of operation simultaneously takes place on the respectivefilter elements.

In FIG. 3, wherein there is shown another embodiment of a distributorconstructed in accordance with the principles of the invention, fourvessels respectively numerically designated 1 1 1 and 1 are fed with thefour different fluids, viz., slurry, second washing, first washing andfresh solvent by four pipes as schematically depicted by arrows 5 6 7and 8 Communicating with and leaving each vessel 1 1 1 and 1., are setsof pipes 9 10 11 and 12 each of these sets correspondingly comprisingfive pipes, viz, 9 to 9e 10:1 to 10e 11:1 to 11e and 12a to 122 Each ofthese pipes leads into a valve, pipes 9a to 92 correspondingly leadinginto valves 13a to 136, pipes 10:2 to 10e leading into the valves 14a to14e, pipes 11:1 to 11e leading into valves 15a to 15e and pipes 12:1 to122 leading into valves 16a to 162. As shown in FIG. 3, all pipes andvalves having the same alphabetic character designation feed the samefilter element respectively. Thus, valves 13a to 16:1 feed filterelement 17, valves 13b to 16b feed filter element 18, valves to 16c feedfilter element 19, valves 13d to 16d feed filter element 20 and valves13e to 16:: feed filter element 21.

If it is assumed that the first fifth of an arbitrarily chosenfiltration cycle begins at a given point and that when it completes afifth of a cycle, the period between such beginning and completion isconsidered a first period, then the tabulation hereinbelow indicates thetiming cycle and order for opening the twenty valves in the distributorof FIG. 3.

Period: Valves concurrently open 1st 13a, 14b, 15c, 16d. 2nd 13e, 14a,15b, 160. 3rd 13d, 142, 15a, 1612. 4th 13c, 14d, 152, 16a. 5th 13b, 14c,15d, 16c. 6th Same as first period.

From the foregoing table it is seen that each respective filter element17 to 21 is sequentially fed With one of the four fluids in four periodof the cycle and is unfed for one period in the cycle, such unfed periodbeing the period that it is overturned.

In FIG. 4, wherein there is shown an embodiment of one filter elementconstructed in accordance with the principles of the invention, there isincluded a vessel 31a having a suitable shape and a bottom and lateralwalls, a grate 32a or other suitable support structure being containedwithin vessel 31a for carrying a filtering cloth thereon. As shown inFIG. 4, vessel 31a may be of rectangular or trapezoidal configurationwith the bottom sloping slightly downwardly toward its center. An outletin the bottom of vessel 31a is connected through a flexible tube 33a toa liquid-separating vessel 34a, vessel 34a being connected to an elementin the collector-separator stage through a pipe 35a and adapted to beconnected to a vacuum source (not shown) through a pipe 36a and a valve50a.

Vessel 31a is supported by a frame 37a and rotatably attached to italong an axis of rotation 38a. Frame 37a is attached to a rotatableshaft 39a which is suitably arranged to rotate on supports affixed to anouter frame (not shown) and onto which, a grooved wheel 40a is keyed inneutral.

Wheel 40a is provided with a tooth 41a on which frame 37a rests and isattached to frame 37a with a wire 42a wound around the outside andaffixed to vessel 31a at one of its ends. Wheel 40a is also controlledby a control mechanism schematically depicted as stage 43a which maysuitably be an externally located mechanical, hydraulic or similar typewinch.

The control mechanism of stage 43a may be, for example an electric motorand a mechanical reduction system having gears, V-belts or chains or thelike, and having reversible movement. The control mechanism, which actsupon the wheel 40a turning about the axis 39a, begins moving in onerotary direction (clockwise in FIG. 4) when it receives an electricpulse signal from the timer 4.

If it is assumed that the filter element shown in FIG. 4 is the onewhich is unfed, when the washing of the cake thereon on the cloth ongrate 32a is completed, mechanical or other type winch 43a commences tooperate to turn wheel 40:: in a clockwise direction on shaft 39a asviewed in FIG. 4, frame 37a cont nually remaining supported by tooth 41aand filter element 31a placed thereon. Frame 37a is rotated to the pointat which lug 44a on and suitably integral with frame 37a encounters lug45a 0n the outer frame in its rotational path. Thereafter, the rotationof vessel 31a with respect to frame 37a commences around axis ofrotation 3811 while wire is concurrently unwound from wheel 40a.

The rotation wheel 40a continues until vessel 31a is completelyoverturned and has reached the position shown in FIG. 4 by the dashedline outline thereof, at such completely overturned position, vessel 31acoming to rest against a support 46a which is attached to the outerframe. For stop-control of the vessel 31a, the support 46a may beprovided with an electric end-of-stroke device such as a solenoid thatstops the winch 43a and subsequently causes the beginning of themovement thereof in the opposite rotary sense (counterclockwise in FIG.4). The filter cake which is discharged from vessel 31a by itsoverturning is collected with the aid of converging slide elements 47aonto a transporting element 48a which effects its removal, the vacuumbeing removed to facilitate discharging through control of the timer.Respective groups of nozzles 49a may be included, disposed as shown inFIG. 4, to periodically produce spouts of water for washing thefiltering cloth once the filter cake has been discharged from vessel 31awhile it is in its overturned state.

The aforementioned nonillustrated end-of-stroke device located atsupport 46a can control the discharge of water from the nozzles 49a forwashing the filter-cloths, the water discharge ending when the filteringelement is again raised to the solid-line position thereof shown in FIG.4.

To raise the filtering element, the rotation of wheel 40a in theopposite direction (counterclockwise) is commenced to take up wire 42aand the rotation of wheel 40a is continued until frame 37a and vessel31a attain their normal upturned initial positions.

Though not illustrated, it should be understood that, besides thefiltering element and associated elements shown in FIG. 3, the filter ofmy invention includes four more similar filtering elements andrespective associated elements. The filtering element of FIG. 4 and itsassociated elements are identified by a reference character having asubscript a and the four nonillustrated filtering elements andrespective associated elements will be identified when referred tohereinafter with the same reference characters respectively, except thatthe subscripts will be b, c, d and e respectively. v

The timer 4 (FIG. 1) provided for the control of filter operation may beofthemechannical or of the electronic type, and should carry out aseries of opera tions of cyclic nature on the valves 11a,.11b, 11c, 11d,he of FIG. 2A, on the filtering elements F to F of FIG. 1 and 31a to 31eas in FIG. 4, and on the valves 50a to 50c (only 50a shown in FIG. 4),connecting the filtering elements 31a to 31e withthe source of thevacuum placed on the tubes36a to 362 (only 36a shown in FIG. 4).

In FIG. 3A there are diagrammatically shown electrical connectionsbetween the timer 4 of FIG. 1 and the just- .mentioned members 11a tolle, 31a to 31e and 50a to 50e. Every cycle of time, after the elapse ofwhich the identical operations are repeated, is subdivided into a numberof equal parts, corresponding to the numberof filtering elements (fivein the illustrated example) which are referred to hereinafter asfractions ofa cycle. During every fraction of a cycle, analogousoperations are performed, which are however, not equal to those of thepreceding fraction. At the beginning of each fraction of cycle (timeT0), the valves 11a, 11b, 11c, 11d, He (opened during the precedingfraction) are closed. During the fraction of cycle, the complete actionof tiltingand relifting the filtering element previously in motion isterminated. One of the valves 50a to 50:: is opened, e.g., valve 50a.The rotation of the corresponding filtering element vessel 31a to 31cbegins with a tilting movement and then follows with a lifting orrestoring movement. At intervals of time predetermined by the timer4,.four of the valves 11a, 11b, 11c, 11d, 112 are opened, in the examplechosen all except the valve 11a.

At the end of the fraction of cycle (time To+AT=T the four open valves11b, 11c, 11d, 11e are closed simultaneously. The sequence of theoperations for the first two fractions of cycle is given in thetabulation hereinbelow in which:

T is the initial instant (moment of time) Az is an adjustable timeinterval, lower than At At is an adjustable time interval, lower than ATAt At At Ar are adjustable time intervals, greater than At, but smallerthan T T and define respectively the beginning of the filtration of thefirst, second and third washing AT=T T =T T etc., is the duration of afraction of period t Y T =start of the cycle with closure of the valves11a, 11b,

11c, 11d previously open T +At =return of filtering element vessel 31c,previously in movement, to the rest position T +At=closure of the valve50e previously open; opening of valve 50a and beginning of the tiltingof vessel 31a with a reciprocatory stroke T +At =opening of valve 11e IT +At =opening of valve 11d i1 Y 1 T +At =opening of valve T+At =openingof valve 11b T (=T +AT) end of the cycle 1 1 (T )'=beginning of thecycle with closureof valves 11b, 11c, 11d, 11:: previously open (T +At=return of 31a to rest position (T -i-At) :closure of valve 50apreviously open; opening of valve 50b and beginning of the tilting ofthe filtering element associated with valve 50a with reciprocatorystroke I o+Atr=openingof valve 11a": If

T +At =opening of valve 112 r T -l-At zopening of valvelld T +Ar:opening of valve 110 T T +AT) end of the cycle In view of the cyclicnature of the timing operation just described, after five fractions ofcycle, the fraction of cycle first described above is repeated exactly.Timers of the mechanical and electronic types adapted to perform theabove-described tasks are known in the art. If the timer is of themechanical type, it may include five coaxially rotating discs, eachindividually provided with an electric contact 72 out of phase with oneanother, which during rotation thereof close the respective circuitscorresponding to the individual operations.

In FIGS. 4B and 4C there are shown two of the rotary discs, and therespective electric contacts are indicated by arrows, which are locatedbetween a rotary part (RI for the first disc, RH for the second disc),and a fixed part (81 for the first disc, SH for the second disc).

The contacts of the rotary parts RI and RII, during their rotation,engage all of the contacts of the respective fixed parts 81 and 811 andcause the activities indicated in FIGS. 4B and 4C. The needle contact ofrotary part R11 is 72 out of phase with that of rotary part RI". Thecontacts 11a to 112 are regularly displaceable since the correspondingcontacts (e.g. 11b of the first disc of FIG. 4B and 11c of the seconddisc of FIG. 40, etc.) are rigidly connected with each other and so arealso the contacts 50a to Stle and 31a to 312 on respectively and 50a toStle 01?, the latter contact being offset 72. The contacts 11a to 112off are fixed. On the discs RI and RII there are indicated, by solidlines, the contact indices shown as an arrow, whereas the contactindices of the nonillustrated underlying discs RIII, RIV and RV areshown by dotted lines. The valves 50a to 50e and 11a to 11c are valvesof the all-or-nothing type, namely of the quick opening and closing typesuch as solenoid or pneumatically controlled valves, as indicated inFIG. 4A.

In FIGS. A, 5B and 5C, wherein there is diagrammatically depicted anillustrative embodiment of a collectorseparator constructed according tothe invention, the output of the filter elements which passes through apipe a as shown in FIG. 4, for example, is fed to thecollector-separator stage through five such pipes respectively as shownby the arrows designated with the notations 35a, 35b, 35c, 35d and 35s.It is realized that the function of the collector-separator stage is tomaintain the four fluids, viz., filtrate and first, second, and thirdwashings, produced at the output of the vacuum filtration stage,qualitatively separated.

In the collector-separator stage, per se, there is provided a vessel 51which may suitably be a toroidal conduit, supported by a frame 52.Vessel 51 and its support 52 are adapted to be rotated by suitablerotating means with respect to a vertical axis, the rotating means beingshown in FIG. 5A as a gear 53 controlled by a control element 54. Thisrotation is suitably synchronized with the rotation of the vessels shownin FIGS. 2A to 2C.

The pipes 35a to 35s feed vessel 51 at five angularly equispaceddifferent points, i.e., 72 between points, which lie in a circleconcentric with the circumferential perimeters of vessel 51. Here again,as with the other structures of the filter, the pipe of pipes 35a to 35ewhich is the outlet for the filter element that is unfed and isoverturned in a given fifth of a cycle has no fluid flowing therethroughfor the feeding thereof into its opposing portion of vessel 51, thefiltrate and first, second and third washings being fed through theother of pipes 35a to 35:; during this given point of the cycle to theportions of vessel respectively there opposing.

With the rotating of vessel 51 of FIGS. 5A to SE in synchronism with therotation of vessel 1' of FIGS. 2A to 2C, during a complete rotation,each of pipes 35a to 35e is sequentially fed with each of the fourliquids and then is not fed in the five subdivisions of a cycle.

To effect the maintaining of the separation of the four liquids fed tovessel 51, it is divided into four compartments by radially disposedbaffles 56a, 56b, 56c, and 56d, each of the resulting four compartmentsbeing provided with an outlet, viz., outlets 57a, 57b, 57c and 57d. The

angular displacements of baffles 56a to 56d with respect to each othercan be chosen such that they arrive beneath pipes 55a to 559respectively when there is a change in the flow of fed liquid from onetype to another. This arrangement is particularly pertinent with regardto baffles 56a, 56b and 56c. However, baflie 56d has to be located suchthat it comes into position beneath a pipe of pipes 55a to 55e when theflow is interrupted just prior to the change to a different fluid flow.With such arrangement, there is enabled the feeding of the same fluidsequentially into any of the four respective compartments into whichvessel 51 is subdivided by baffles 56a to 56d whereby there alwayspasses through outlets 57a to 57d respectively the same of the fourfluids, each outlet, of course, having flowing therethrough a differentone of the fluids.

A collector in the collector-separator stage comprises four fixedtoroidal ducts 58a, 58b, 58c, and 58d concentrically coplanarly disposedwhich collects the liquids flowing through outlets 57a to 57d and whichdischarges these liquids through pipes 59a, 59b, 59c and 59d into fourvessels 60a, 60b, 60c and 60d from which they are adapted to be removedby a suitable pumping arrangement (not shown), the filtrate and thirdwashings being eliminated and the first and second washings beingrecycled to the distributor.

In FIG. 6 wherein there is shown another embodiment of acollector-separator, the five pipe outlets from the filter elements,viz., pipe 35a to 352 each multifurcate into four subdivisions, i.e.,pipe 35a subdivides into pipes 61a to 64a, pipe 351) subdivides intopipes 61b to 6412, pipe 35c subdivides into pipes 610 to 64c, pipe 35dsubdivides into pipes 61d to 64d, and pipe 35e subdivides into pipes 612to 64:2. Each of these pipes lead into valves respectivelycorrespondingly designated by the same alphabetic character notation,i.e., pipes 61a to 64a lead into valves 66a to 69:1, pipes 61b to 64];lead into valves 66!) to 6%, pipes 610 to 640 lead into valves 66c to690, pipes 61d to 64d lead into valves 66d to 69d and pipes 61e to 64clead into valves 66? to 69e.

Since four of the five pipes 35a to 35s concurrently discharge fourdifferent liquids respectively, by opening the valves shown in FIG. 6 inaccordance with the hereinbelow set forth tabulation while the totalvalve operation period is synchronized with the feeding and overturningof the filter elements, there is effected the maintaining of separationbetween the four different liquids and the separate collecting thereofin four different vessels 70, 71, 72 and 73 respectively.

The sequence of valve openings tabulation follows. As previouslyutilized hereinabove, the term period signifies one-fifth of a cycle.

Period: Valves concurrently open 1st 66a, 67b, 68c, 69d, 69c. 2nd 662,67a, 68b, 69c, 69d. 3rd 66d, 67e, 68a, 69b, 69c. 4th 66c, 67d, 68e, 69a,6%. 5th 66b, 67c, 68d, 69e, 69a 6th Same as first period The differentliquids respectively collected in vessels 70 to 73 are suitably removedtherefrom by a pumping arrangement not shown and disposed of or recycledas required. Thus, if the filtrate and third washing are received invessels 70 and 71 respectively and the second and first washings arerespectively received in vessels 72 and 73, the contents of vessels 70and 71 are disposed of and the contents of vessels 72 and 73 arerecycled to constitute the first and second washings fed to thedistributor.

Example Filtering of a slurry coming from a phosphoric acidmanufacturing plant is carried out in a filter composed of six filteringelements (one in reserve) each having an area of five square meters. Theslurry has the following composition:

liquid50 tons/hour, specific gravity 1.3 kg./dm. with 30% of P 70 C.;

solid30 tons/hour, specific gravity 2.7 kg./dm. essentially CaSO -2H O.

The feeder distribution stage 1 of FIG. 1 receives four different flowswhich are:

the above-mentioned slurry (A) having a flow rate of 80 tons/hour or49.6 cubic meters/hour;

fresh solvent (B), Water at 60 C. at 35 cubic m./hr.

first washing (W1) coming by pump from the collector stage 3 with flowrate of 36 tons/hour (35.5) cubic meters/hour) and second washing (W2)coming by pump from the collector stage 3 with a flow rate of 40 tons/hour (36 cubic meters/hour).

The feeder distributor feeds the four liquids by natural gravity flow tofour of the five filtering elements, namely the operative elements F F FF in the stage 2 (FIG. 1).

Th rotation of the feeder-distribution lasts four minutes and thirtyseconds altogether, and the period of the timer controlling the valvesis identical; during that rotation, each filtering element receivessuccessively the four individual fluids in amounts corresponding to theflow rates given above for a duration of 54 seconds.

In each operation of 4 minutes and 30 seconds duration there is thusfiltered, washed and discharged an amount of 450 kg. of gypsumsimultaneously in five different filtering elements. From the filteringelements, passing through the vessel 34a of FIG. 4, four different flowsissue by natural gravity at the collector stage 3, namely:

20 tons/hour (=15.4 cubic meters/hour) of filtrate Y with 30% of P 0(namely 6 tons/ hr. of P 0 which constitutes the product coming from thefiltration of the slurry;

44.3 tons/ hour (=37.5 cubic meters/hour) of third washing Z, whichcomes from the cakes washed with the second washing W2 and recycles tothe exterior, to the location of the reaction between sulfuric acid andphosphate rock;

40 tons/ hour (=36 cubic meters/ hour) of second washing W2 coming fromthe cakes Washed with the first washing W1 and which recycles to thefeeder collector stage; and

36 tons/hour 35.5 cubic meters/ hour) of first washing W1 which comesfrom the cakes washed with the fresh solvent B (water) and recycles tothe feeder collector stage.

The liquids are taken up at the outlet of the collector stage from whichthey leave by gravity, and by means of a pump they are conveyed to theaforementioned locations (also see FIG. 1). In this manner, it ispossible to filter 144 tons/ day of P 0 Every 2 days or so the filteringcloths became clogged and must be washed thoroughly or replaced. To thatend, about every 10 hours one of the filtering elements previously usedwas replacedby the reserve filtering element, and the cleansing orreplacing of the cloths was then carried out, taking about 2 or 3 hours.After this cleansing the reserve element was returned to reserve status,and thereby was made available for any unforeseen damage of anotherelement. Thus a possibility is afforded to completely avoiding anystoppage or shutdown for long periods of time.

From the foregoing it is seen that in accordance with the invention,there is provided a filter which is relatively mechanically simple andin which relative movements between feeding members and filteringelements and sliding seals for the separating of liquids are completelyeliminated. Nor can deposits form therein.

It will be obvious to those skilled in the art upon studying thisdisclosure that filters according to this invention permit of a greatvariety of modifications and hence can be given embodiments other thanthose particularly illus- 12 trated and described herein withoutdeparting from the essential features of the invention and within thescope of the claims annexed hereto.

What is claimed is:

1. A continuously operative vacuum filter capable of effecting afiltration of a slurry and a 'given number of subsequent backwashings offilter cake with said given number of different washing fluidscomprising: a vacuum filtration stage comprising a chosen number offilter elements, said chosen number exceeding, said given number by atleast two, each of said filter elements including a normally uprightvessel, outlet means for discharging filtrate fluid therefrom andadapted for connection to a vacuum soucre and control means associatedwith said vessel and operative to be actuated to place said vessel in anoverturned position and to restore it from said overturned back to itsupright position while cutting it off from said vacuum source; afeeder-distributor stage comprising means for separately receiving saidslurry and each of said washing fluids, means for concurrently feedingone of said slurry and said washing fluids to each of said respectivefilter elements during a given time period which is an equal subdivisionof a time cycle consisting of said chosen number of time periods and forsequentially feeding said slurry and said washing fluids in apredetermined order to each of said rfilter elements whereby during eachtime cycle, each filter element sequentially receives said slurry andeach of said washing fluids in said predetermined order and is unfedduring one period of said cycle and whereby said slurry and each of saidwashing fluids are respectively sequentially fed to different filterelements respectively and each of said filter elements is respectivelyunfed in successively occurring time periods; a collector stage forreceiving the fluid otuputs from said filter elements and for separatelycollecting them, said collector stage including said chosen number lessone of collecting vessels and means for directing the same fluids fromsaid fluid outputs into only respective ones of said vessels; and timingmeans for controlling the sequential feeding of said fluids and saidslurry to said filter elements for controlling the actuation of saidfilter element vessels control means during said unfed periods, and forcontrolling the cutting off of said respective filter elements from saidvacuum source during said unfed periods.

2. A continuously operative vacuum filter capable of etfecting afiltration of a slurry and n subsequent sequential backwashings of thefilter cake resulting from said filtration with n washing fluidscomprising: a vacuum filtration stage comprising n+2 filter elements,each of the filter elements comprising a normally upright vessel, outletmeans communicating with said vessel for discharging fluid therefrom andadapted for connection to a vacuum source and control means associatedwith said vessel and operative to be actuated to place said vessel in anoverturned position and to restore it from said overturned position backto its upright position while cutting it off from said vacuum source; afeeder-distributor stage comprising means for separately receiving saidslurry and each of said washing fluids, means for concurrently feedingone of said slurry and said washing fluids to each of said respectivefilter elements during a given time period which is an equal subdivisionof a time cycle consisting of said n+2 time periods and for sequentallyfeeding said slurry and said washing fluids in a predetermined order toeach of said filter elements whereby during eachtime cycle, each filterelement sequentially receives said slurry and each of said washingfluids in said predetermined order and is unfed during one period ofsaid cycle and whereby said slurry and each of said'washing fluids arerespectively sequentially fed to dilferent filter elements respectivelyand each of said filter elements is respective ly unfed in successivelyoccurring time periods; slurry, filtrate fluid and first to nth washingfluids being produced from said filter elements; a collector stage forreceiving the fluid outputs from said filter elements and for separately collecting them, said collector stage including n+1 collectingvessels, means for directing the same fluids from said filter elementsfluid outputs into only respective ones of said collecting vessels, andmeans for recycling chosen ones of said filter elements washing fluidsoutputs as said washing fluids fed to said feeder-distributor stage, andtiming means for controlling the sequential feeding of said fluids andsaid slurry to said filter elements for controlling the actuation ofsaid filter element vessels control means during said unfed periods, andfor controlling the cutting otf of said filter elements from said vacuumsource during said unfed periods.

3. A continuously operative vacuum filter as defined in claim 2 where nis equal to 3 and said washing fluids comprise a fresh solvent, a secondwashing fluid and a first washing fluid, the predetermined order offeeding said fluids to a filter element being slurry, second washingfluid, first washing fluid and fresh solvent, said first washing fluidresulting from the washing of said filter cake with said fresh solvent,said second washing fluid resulting from the washing of said cake withsaid first washing fluid, said first and second washing fluids producedfrom said filter elements being said fluids recycled to saiddistributor.

4. A continuously operative vacuum filter as defined in claim 2 whereinsaid timing means is operative to control said sequential feeding ofsaid fluids to said respective filter elements only after the fluids fedin the period immediately preceding a given period feeding have beendischarged from said elements to thereby insure the sepa ration of saidfluids.

5. A continuously operative vacuum filter as defined in claim 2 whereinthere is further provided n+1 conduits for feeding said slurry and saidwashing fluids to said feederdistributor stage and wherein saidfeeder-distributor stage comprises n+1 containers in opposingrelationship with the ends of said conduits for receiving the slurry andfluids therein respectively, outlet means from each of said containers,each of said outlet means multifurcating into n+2 tu-bes respectively,time controlled (n+1) (nH-Z) valves for each of said tubes to dischargethrough respectively corresponding ones of each of said tubes and theirassociated valves arranged to discharge into one of said filterelements, the timing of the openings and closings of said valves beingcontrolled whereby nH- I of said filter elements concurrently receives adiflerent one of said slurry and one remains unfed and whereby each ofsaid slurry and said fluids are sequentially fed to said filter elementsrespectively in successively occurring time periods.

6. A continuously operative vacuum filter as defined in claim 2 whereineach of said filter elements comprises a normally upright filteringvessel for receiving each of said slurry and said fluids sequentiallyrespectively from said feeder-distributor stage during successivelyoccurring periods, a frame for supporting said vessel, said vessel beingrotatably attached to said frame along an end edge thereof, rotatablemeans operatively associated with said frame and said vessel forrotating in opposite directions said frame and vessel vertically about ahorizontal axis near the other end of said frame, first stop meansdisposed to halt the rotation in one direction of said frame about saidaxis after about 90 of said rotation, whereby said vessel rotates aboutsaid one edge to an overturned position, second stop means for haltingthe rotation of said vessel when it is in a substantially overturnedhorizontal position, and means included in said rotating means which inresponse to the rotating of said rotating means in the directionopposite to said one direction restores said vessel to its supportedposition on said frame and restores said vessel and support to saidupright position, said rotating means being controlled by said timingmeans to be actuated into said rotations during the unfed period of saidfilter element, a container, conduit means connected between said vesseland said container for discharging the filtrate fluid from said vesselinto said container, first outlet means from said container to connectsaid container to a vacuum source and second outlet means from saidcontainer to feed said filtrate fluid to said collector stage.

7. A continuously operative vacuum filter as defined in claim 2 whereinthere are further included n+2 conduit means for discharging therespective fluid outputs from said filter elements and wherein saidcollector stage comprises n+1 pipes multifurcating from each of saidlast named circuit means respectively, (nH-l) (n+2) time controlledvalves, each of said valves being associated with one of said tubes, n+1containers for receiving the fluid discharged through groups ofcorresponding ones of said tubes and said valves, the opening andclosing times of said valves being time controlled whereby each of saidcontainers always receives the same fluid from said filter elements.

8. A continuously operative vacuum filter as defined in claim 2 whereinthere is further provided n+1 conduits for feeding said slurry and saidwashing fluids to said feeder-distributor stage and wherein saidfeeder-distributor stage comprises a container having said n+2compartments, each of said conduits being opposed to and positioned todischarge into all but one of said compartments respectively, meansassociated with said container and operative in response to the controlof said timing means for synchronously rotating said container at a rateof one rotation per said time cycle whereby each of said compartments isin opposing relationship with each of said conduits for one periodduring said cycle to sequentially be fed the n fluids and the slurrytherefrom and is unfed for one period, n+2 outlet means communicatingwith and leading from each of said compartments respectively, and n+2means for feeding the fluids from said conduits to correspondingrespective filter elements whereby each of said filter elements issequentially fed said slurry and said fluids during n+1 periods of saidcycle and remains unfed during one period of said cycle and whereby eachof said slurry and fluids are sequentially fed to each of said filterelements.

9. A continuously operative vacuum filter as defined in claim 8 whereinsaid means for feeding said fluids from said conduits to said filterelements comprises n+2 concentrically planarly disposed ducts into whichsaid outlet means respectively discharge, n+2 receptacles, n+2 pipesconnecting said ducts to said receptacles respectively to discharge thecontents of said ducts into said receptacles, and n+2 time controlledvalves connected between respective receptacles and filter elements, theopenings and closings of said valves being timed whereby one of saidslurry and fluids is fed from a receptacle to a filter element onlyafter the immediately preceding fed fluid has been discharge throughsaid filter element,

10. A continuously operative vacuum filter as defined in claim 8 whereinthere are further included n+2 conduit means for discharging therespective fluid outputs from said filter elements and wherein saidcollector stage comprises a vessel adapted to be rotated along avertical axis and divided into n+1 compartments which are disposed toreceive the fluid from said respective conduit means, each of said othercompartments being disposed to receive the respective fluids from eachof said other conduit means, n+1 tubes communicating with and leadingfrom each of said compartments and n+1 containers for respectivelyreceiving the fluid discharged through one of said tubes, meanscontrolled by said timing means for rotating said vessel in synchronismwith the rotation of the container of said feeder-distributor stage, therespective sizes of said compartments and indexing of said container forrotation being so chosen whereby the one of said compartments whichcomes into position opposite two of said conduit means concurrentlyduring one of said periods receives only one of the fluids from saidfilter elements through one of said last named conduit means, the otherof said last named conduit means being from the filter element which isunfed during said last named one period whereby each of saidcompartments and said containers always receives the same fluid.

11. A continuously operative vacuum filter as defined in claim 8 whereinsaid collector stage vessel is a toroidal duct and wherein there arefurther included n +1 concentrically horizontally planarly disposedtoroidal receptacles, each of said tubes being connected 'betwen one ofsaid compartments in said duct and one of said toroidal receptacles, andn+1 tubes connected respectively between one of 'said toroidalreceptacles and one of said containers.

References Cited REUBEN FRIEDMAN, Primary Examiner.

F. SPEA=R,' Assistant Examiner.

